Prior to setting forth the background of the invention in detail, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “Computer to plate” (hereinafter: CTP) as used herein in this application, relates to an imaging technology used in modern printing processes. In this technology, an image created in a Desktop Publishing application is output directly to a printing plate. CTP as used hereinafter relates also to the imaging device carrying the process of outputting the computer-stored image on the printing plates.
The term “Printing Plates” (sometimes referred to as “plate” or “plates”) as used herein in this application, relates to the flexible aluminum or plastic plates that are used in off-set printing technology. Traditional printing plates have a brushed or roughened texture and are covered with a photosensitive emulsion. A photographic negative of the desired image is placed in contact with the emulsion and the plate is exposed to light. After development, the emulsion shows a reverse of the negative image, which is thus a duplicate of the original (positive) image. The image on the plate emulsion can also be created through direct laser imaging in a CTP imaging device. Printing plates are typically stacked in a cassette, on a pallet or similar container which houses the plates and facilitates their protection, transportation, and handling, before loading them into a dedicated tray within a CTP imaging device.
Every CTP imaging device usually comprises trays for accommodating the printing plates exhibiting specific dimensions. Trays can usually be arranged to contain plates of various sizes, but all plates in the same tray are of one size. The plates may be manually removed from the cassette, pallet or a shipping container and then inserted into the trays for use by the CTP imaging device.
After the plates are loaded into a CTP imaging device tray and prior to the plate loading, the slip sheet is removed from the loaded plate. According to the traditional art, the slip sheet is removed from the CTP device using a slip sheet disposal system.
As the top plate positioned on the plate stack is often not positioned perfectly relatively to the plate stack, an alignment process has to be performed in order to position the top plate so that it is properly aligned for the plate picker operation.
According to the traditional art, a system for handling printing plates will generally use trays or plate pallet, the plates having specific dimensions. Different trays can usually be set to contain plates of various sizes, but all plates in a single tray will be in the same size. The plates can be picked automatically from the relevant trays or directly from the originally packed plate pallet and loaded into the imaging device for imaging. There is a widely recognized need for an automatic and efficient handling system for feeding plates directly from the original plate pallet into the imaging device, while maintaining precise alignment of the plate during the plate loading process.
FIG. 1 describes a pallet alignment and picker apparatus 10 according to the prior art. The top plate 13 is positioned on top of a plate pallet 14 (or a plate stack). Top plate 13 is often shifted slightly in respect to the plate pallet due to manual handling of the plate stack or pallet.
This manual process introduces inherent position inaccuracies in picking the top plate, in respect to the plate picker 11. Plate picker 11 is configured to pick a top plate 13 and load it into a CTP imaging device 20 (Shown in FIG. 2). The top plate 13 should be perfectly aligned with the plate picker position 12 in order to load plate 13 in a perfect position into the imaging device 20.